1. Field of the Invention
The invention relates to a method of teaching robot movements.
2. Description of the Prior Art
Programmable robots are commonly used for a variety of repetitive industrial applications. As appreciated, a robot only performs tasks and motions that are preprogrammed. Programming of robot motions can be a complicated and time-consuming process. Methods of reducing programming time include programming robot motions by lead through teaching. Typical lead through teaching methods include the steps of moving the robot through a set of desired motions, sensing specific points during the movement of the robot, recording the specific points in a microprocessor, and utilizing the recorded points to create movement commands. The robot repeats the desired motions according to the created movement commands. An operator programming a robot utilizing a lead through teach method is responsible for guiding the robot and for maintaining the desired position and orientation of the robot in three or more dimensions. A drawback to conventional lead through teach methods is that an operator must constantly guide the robot through motions burdened with the requirement to accurately guide the robot through the desired motion while never allowing a collision with an object in the workspace and never allowing the robot to apply excessive pressure to the workpiece. As shown in FIG. 1, the operator polishing a small mold 26 can easily manipulate a hand held polishing tool 28. Referring to FIG. 2, when the same polishing tool 28 is attached to an end of the robot 12, the task becomes burdensome to the operator and intuitive movements by the operator made with the polishing tool 28 become difficult, resulting in less then desirable programmed movements of the robot 12. Additionally, the mold 26 can be damaged if the polishing tool 28 errantly crashes with the mold 26 or applies excessive pressure to the mold 26 due to the operator's inability to overcome the inertial forces of the robot 12 or to otherwise guide the robot 12 along the desired path.
Improvements on this method include the use of various types of teaching handles (not shown) that aid the operator in guiding the robot through the desired motions. Teaching handles improve the operator's mechanical advantage over the robot, however the operator is still left to manipulate and accurately control the robot through the desired motions while maintaining control in three or more dimensions.
Further, some applications require that an end of arm tool be controlled within a tight tolerance relative to the workpiece. Robots are known to utilize a touch sensor that contacts the workpiece during operation. U.S. Pat. No. 5,906,761 to Gilliland et al. utilizes a touch sensor incorporated into a tip of a welding torch. The touch sensor allows the robot to maintain a predetermined distance between the welding tip and the workpiece during welding operations. However, the predetermined distance is maintained during the welding operations not during the teaching of the robot, thereby still leaving the burdensome task to the operator of accurately guiding the robot during teaching.
Consequently, there is a need for a method that allows the operator to teach robot motions while concurrently maintaining a spatial relationship between the robot and the workpiece. Further, it is desirable to free the operator from having to guide the robot in three dimensions during teaching operations in an effort to reduce the complexity of programming desired motions of the robot. Further, simplification of the teaching operation allows for more efficient teaching of robot motions, making additional uses of programmable robots economically feasible.